Serialization Program

/*
Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or
transmitted across a network connection link to be reconstructed later in the same or another computer environment.
Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization
algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.
For example, you may serialize the following tree
    1
   / \
  2   -3
     / 
    1

inorder: [2] 1 [[1] -3] : (2 1 1 -3) 
pre-order: 1 [2] [-3 1] : (1 2 -3 1)  


recover
inorder:  (2 1 1 -3) 
pre-order: (1 2 -3 1)  

1[2[][]][-3[1][]]

*/

#include <bits/stdc++.h>
using namespace std;

struct node{
  
  int val;
  node* left;
  node* right;
  node(int v):
    val(v)
  {
      left = nullptr;
      right = nullptr;
  }
};


std::string serialize(node * root){
  
  if(root==nullptr){
    return "";
  }
  auto l = serialize(root->left);
  auto r = serialize(root->right);
  
  return std::to_string(root->val)+"["+l+"]["+r+"]";
}


node* deserialize(const std::string& s){
  
  if(s.length()<1)return nullptr;
  //std::cerr << s << "\n";
  
  std::size_t first = s.find("[");
  int opens=1;
  int i;
  for(i=first+1;i<s.length();i++){
    if(s[i]=='['){
      opens++;
    }else if(s[i]==']'){
      opens--;
    }
    if(opens==0)break;
  }
  //std::cerr << i << " " << first << "\n";
  auto left = deserialize(i==first+1?"":s.substr(first+1,i - first-1));
  //std::cerr << i << " " << first << "\n";
  
  i+=2;
  int second = i;
  opens=1;
  for(;i<s.length();i++){
    if(s[i]=='['){
      opens++;
    }else if(s[i]==']'){
      opens--;
    }
    if(opens==0)break;
  }
  auto right = deserialize(second==i?"":s.substr(second,i - second));
  
  node * root = new node(std::stoi(s.substr(0,first)));
  root->left = left;
  root->right = right;
  
  return root;
  
}


int main(){
    
  node * r = new node(1);
  
  r->left = new node(2);
  r->right = new node(-3);
  r->right->left = new node(1);
  
  std::string st = serialize(r);
  std::cerr << st << "\n";
  
  auto recover = deserialize(st);
  
  
  
  return 0;
  
}